This invention relates to photographic compounds, such as couplers, that comprise a novel group capable of being released during photographic processing, and to photographic materials and processes using such compounds.
Images are commonly obtained in the photographic art by a coupling reaction between the development product of a silver halide color developing agent, particularly an oxidized aromatic primary amino developing agent, and a color forming compound commonly described as a coupler. The dyes formed vary depending upon the composition of the coupler and the developing agent. The subtractive process of color formation is typically employed in multicolor photographic elements Resulting dyes are typically cyan, magenta and yellow dyes formed in or adjacent to silver halide layers sensitive to radiation complementary to the radiation absorbed by the image dyes, that is, silver halide emulsions sensitive to red, green and blue radiation.
Compounds that release a group, particularly couplers that release a coupling-off group, are known in photographic materials, such as those described in U.S. Pat. No. 3,935,015; 4,483,918; and 4,853,319. Such compounds often do not have the desired degree of stability in such photographic materials, particularly during storage before exposure. It is important to choose coupling-off groups which provide the desired increase in coupling reactivity, but which do not cause undesired losses in sensitometric effects or in the stability of the resulting image dyes
There has been a need for a new class of compounds, particularly dye-forming couplers, that comprises a group that is capable of being released upon processing in a photographic silver halide material such that the coupler has a higher activity (gamma) and the dye image obtained on color processing has increased resistance to changes caused by heat, light and humidity.